A radio base station uses handover control that finds a new baseband resource (destination baseband resource) capable of allowing a call communicating in a baseband resource to autonomously continue the communication and thus allows the call to continue the communication by using this new resource.
With reference to FIGS. 5 through 8, the following describes non-instantaneous-disruption hard handover control (hereinafter referred to as non-instantaneous-disruption HHO) in a radio base station (hereinafter referred to as Node-B) specified in the conventional 3rd Generation Partnership Project (hereinafter referred to as 3GPP) TS25.433.
FIG. 5 shows a non-instantaneous-disruption HHO sequence between a radio network controller (hereinafter referred to as an RNC) and a Node-B. FIG. 6 shows details of a radio link reconfiguration commit message sent from the RNC to the Node-B. The non-instantaneous-disruption HHO sequence in FIG. 5 occurs when the Node-B establishes a new radio link. At this time, it is assumed that a radio synchronization link configuration procedure is completed normally. Upon completion of the radio synchronization link configuration procedure, the Node-B changes the radio link using a connection frame number (hereinafter referred to as a CFN) that arrives next. As shown in FIG. 6, the CFN is contained in the radio link reconfiguration commit message from the RNC. The radio link handover using the CFN completes the non-instantaneous-disruption HHO.
With reference to FIGS. 7 and 8, the following describes the non-instantaneous-disruption HHO performed for a call communicating in the baseband resource, by using a baseband signal block 706 in a Node-B 703 according to CFN notification from an RNC 711. FIG. 7 is a block diagram showing the configuration of a conventional mobile communication system using the CDMA technique. FIG. 8 is a block diagram showing the configuration of the baseband signal block 706 in FIG. 7. For communication in the mobile communication system using the CDMA technique as shown in these diagrams, the RNC 711 first establishes a radio link with a call-process/maintenance-process monitoring block 709 in the Node-B 703 via a wired transmission path 710. The radio link information is temporarily stored in the call-process/maintenance-process monitoring block 709 in the Node-B 703, and is then transferred to a search block 802a, a rake block 803a, and a codec block 804a (FIG. 8) in a baseband resource A 801a of the baseband signal block 706.
The following describes processings in an upstream signal line 805. An upstream signal from a mobile station 701 is input to an RX unit of a TX/RX AMP unit 704 in the Node-B 703 via a radio transmission path 702 and is A/D converted in an A/D & D/A conversion block 705. The converted signal is transferred to a baseband resource A 801a in the baseband signal block 706 via the upstream signal line 805. The baseband resource A 801a allows the search block 802a to perform multi-path detection and path tracking. The baseband resource A 801a then allows the rake block 803a to perform channel estimation, SIR detection, and RAKE combination. The baseband resource A 801a then allows the codec block 804a to perform a decode process (error correction process) for the RAKE-combined upstream signal and perform downstream transmission power control. The decoded upstream signal is transferred to an ATM cell composition block 707 for ATM cell conversion. A transmission I/F black 708 band-limits the ATM cell for each signal. The signal is then transmitted to the RNC 711 via the wired transmission path 710.
The following describes processings in a downstream signal line 806. A downstream signal from the RNC 711 is input to the transmission path I/F block 708 via the wired transmission path 710. After the ATM cell is detected, the downstream signal is transferred to the ATM cell composition block 707 for ATM cell conversion. The downstream signal is then input to the baseband resource A 801a in the baseband signal block 706 via the downstream signal line 806. The baseband resource A 801a allows the codec block 804a to perform encoding processes (CRC generation process and error correction process) and upstream transmission power control for the downstream signal. The encoded downstream signal is D/A converted in the A/D & D/A conversion block 705. The downstream signal is transferred to the TX section of the TX/RX AMP unit 704 and then is transmitted to the mobile station 701 via the radio transmission path 702.
The above-described processings are likewise performed in another baseband resource B 801b (search block 802b, rake block 803b, codec block 804b) disposed in the baseband signal block 706. During communication of upstream signals/downstream signals, the call-process/maintenance-process monitoring block 709 manages call processings and maintenance processings in the Node-B 703.
The following describes processings for the non-instantaneous-disruption HHO performed by the Node-B 703 according to notification from the RNC 711. In accordance with notification from the RNC 711, the Node-B 703 performs the non-instantaneous-disruption HHO for a call communicating in the baseband resource A 801a in the baseband signal block 706. At this HHO, the RNC 711 establishes a new radio link with the call-process/maintenance-process monitoring block 709 via the wired transmission path 710. The call-process/maintenance-process monitoring block 709 is then notified of the CFN as non-instantaneous-disruption HHO timing via the wired transmission path 710.
The new radio link configuration and the CFN information are temporarily stored in the call-process/maintenance-process monitoring block 709 and are transferred to the search block 802a, the rake block 803a, and the codec block 804a in the baseband resource A 801a in the baseband signal block 706. The search block 802a, the rake block 803a, and the codec block 804a store therein the notified new radio link information and the CFN. These blocks switch the signal processings between upstream line signals and downstream line signals so as to perform processings based on the radio link information before the configuration until the CFN−1 timing is notified and to perform processings based on the new radio link information after the CFN timing is notified.
For generating the CFN which functions as non-instantaneous-disruption HHO timing, it is performed to compare the upstream CFNs used in the search block 802a, the rake block 803a, and the codec block 804a for upstream line signals with the downstream CFN used in the codec block 804a for downstream line signals.
During the signal processings for upstream line signals, the search block 802a calculates an upstream CFN (regularly updated every 10 ms per radio frame) from the reference frame timing for multi-path detection. The search block 802a compares the calculated upstream CFN with the notified CFN. The rake block 803a calculates an upstream CFN (regularly updated every 10 ms per radio frame) to be used as the reference frame timing for RAKE combination. The rake block 803a compares the calculated upstream CFN with the notified CFN. The codec block 804a calculates an upstream CFN (regularly updated every 10 ms per radio frame) to be used as the reference frame for RAKE-combined data transferred from the rake block 803a during the decoding process. The codec block 804a compares the calculated upstream CFN with the notified CFN. These blocks each calculates and stores upstream CFN calculation timing. As a result, an information transfer delay can be limited to an allowable range. Thus, the upstream line signal can be switched without an instantaneous disruption.
During the signal processing for downstream line signals, the codec block 804a calculates: CFN information concomitant with the downstream signal converted into the ATM cells in the ATM cell composition block 707; and the downstream CFN (regularly updated every 10 ms per radio frame) to be used as the reference frame during the encoding processes. The codec block 804a compares the calculated upstream CFN with the notified CFN. If there is no downstream line signal converted into ATM cells, the codec block 804a switches the downstream line signals based on the CFN to be used as the reference frame for the autonomous code process. The codec block 804a calculates and stores the downstream CFN calculation timing. Since no information transfer is performed, downstream line signals can be switched without an instantaneous disruption.
The non-instantaneous-disruption HHO process uses the baseband resource A 801a before the HHO occurring. The resource stores therein the information needed before the handover timing such as acquired path information in the search block 802a and transmission-power control information in the codec block 804a. That is, the non-instantaneous-disruption HHO can be easily implemented so long as the search block 802a, the rake block 803a, and the codec block 804a respectively keep track of the CFN occurring as the handover timing.
However, there is another hard handover control technique wherein the Node-B 703 finds a new destination baseband resource capable of continued communication for a call communicating in the source baseband resource and allows the call to communicate using the new resource. That hard handover control corresponds to the drive-out control, one of the maintenance functions of a radio base station.
Since the Node-B 703 autonomously performs the drive-out control, a then-communicating call requires hard handover without a instantaneous disruption. General procedures are specified for each Node-B 703 and may allow a situation where the instantaneous disruption is inevitable. Currently, there is no specified procedure used as the reference for unification. The drive-out control is also expected to reliably implement the non-instantaneous-disruption HHO without affecting a communicating call.